This invention relates to an unloading device for shipping containers, such as trucks. More particularly, this invention relates to an apparatus for pulling a load from a container.
The transportation and storage of large or heavy objects is carried out in many instances by loading the objects in a truck or storage container. Fiberglass insulation batts, for example, are highly compressed and packaged in large packages for shipping from a manufacturing facility to a distribution or storage location or to a site of installation. These large, heavy packages are often bulky and present difficulties in loading and unloading the truck or storage container. To load the storage container, the packages are placed side by side in the container, and multiple rows and tiers of the packages are placed within the container, filling it with as little as one row, or tier, up to a full container load. A half load of such insulation material may weigh as much as 10,000 pounds.
The unloading of this material is accomplished by a variety of methods, including manual unloading, and unloading with the aid of a mechanical lifting device, such as a forklift. The material can be unloaded at a location with a loading dock. However, unloading is often necessary at locations that are not equipped with a loading dock. Conventional unloading practices usually involve removing one package at a time until the container is unloaded. This method is both time-consuming and requires a tremendous amount of physical effort by the person unloading the container. As more and more of the load is removed from the container, it is necessary to move each row of material to the end of the container before finally removing the material from the container. This movement of the material within the container is often referred to as tailgating. Manual unloading of the material in the container on a piece-by-piece basis is costly, and the additional physical effort by the unloader during the tailgating movement of the packages further increases the labor cost, thus resulting in increased shipping costs. An additional known method for unloading a shipping container includes the use of a rolling floor and push plate mechanism, as evidenced by U.S. Pat. No. 5,395,204 to Balik. Another known method for unloading a load from a container involves the use of a conveyor belt contained within the trailer, in combination with a rolling floor and pushing mechanism, as evidenced by U.S. Pat. No. 3,998,343 to Fors. It is also known to use a trailer-contained conveyor system in conjunction with a bulkhead which moves beyond the back opening of the trailer, as evidenced by U.S. Pat. No. 4,842,471 to Hodgetts. While all of these additional methods reduce physical effort and unloading time, all require specially equipped shipping containers, thus substantially increasing shipping costs by requiring specialized equipment.
It is known to use a sheet or belt laid over the bed or floor of the storage container in conjunction with a conveyor system to remove a load from a container, as evidenced by U.S. Pat. No. 4,749,325 to Hodgetts. The method suggested by this patent includes pulling the load from the container by pulling a sheet laid over the bed of the container along the conveyor mechanism and winding this sheet around a mandrel to pull the sheet and the load out of the container.
It would be advantageous if a method could be developed to increase the ease with which a load of various materials could be effectively removed from a truck or other container without requiring time-consuming physical unloading of the container and without requiring the use of costly customized unloading equipment.
The above objects as well as other objects not specifically enumerated are achieved by an apparatus for unloading a load from a container having a floor, where the apparatus includes a floor sheet placed on the floor of the container, the floor sheet having a top surface with a coefficient of static friction less than about 0.3. A pull sheet is placed on the top surface of the floor sheet, the pull sheet having a bottom surface with a coefficient of static friction less than about 0.5. The pull sheet has a tensile strength sufficient to enable the pull sheet to be pulled from the container while maintaining the load on the top surface of the pull sheet to unload the load from the container.
According to this invention, there is also provided a method of unloading a load from a container having a floor, including positioning a floor sheet on the floor of the container, the floor sheet having a top surface with a coefficient of static friction less than about 0.3. A pull sheet is positioned on the top surface of the floor sheet, the pull sheet having a bottom surface with a coefficient of static friction less than about 0.5. A load is placed on a top surface of the pull sheet. The pull sheet is pulled from the container while maintaining the load on the top surface of the pull sheet to unload the load from the container.
According to this invention there is also provided a method of unloading a load from a container having a floor, including positioning a floor sheet on the floor of the container, the floor sheet having a top surface with a coefficient of static friction less than about 0.3. A pull sheet is positioned on the top surface of the floor sheet, the pull sheet having a load portion and an extension portion, the load portion having a bottom surface with a coefficient of static friction less than about 0.5 and being adapted to receive the load, and the extension portion being adapted to extend away from the load portion for pulling the pull sheet from the container. A load is placed on a top surface of the pull sheet, and the extension portion is extended. The pull sheet is pulled from the container by pulling the extension portion relative to the container while maintaining the load on the top surface of the pull sheet to unload the load from the container.
According to this invention, there is also provided a method of unloading a load from a container having a floor, the container having a rearward end and the load having a forward end in a direction opposite the direction of the rearward end of the container. The method includes positioning a floor sheet on the floor of the container, the floor sheet having a top surface with a coefficient of static friction less than about 0.3. A pull sheet is positioned on the top surface of the floor sheet. The load is positioned on the pull sheet. The load is unloaded from the container by applying a rearwardly directed force to the forward end of the load.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.